Integrins are heterodimeric integral membrane proteins composed of an alpha chain and a beta chain. The I-domain containing CD51 / Integrin alpha-V undergoes post-translational cleavage to yield disulfide-linked heavy chain (125 kDa) and light chain (25 kDa), which combine with multiple integrin beta chains to form different integrins. Among the known associating beta chains (beta chains 1,3,5,6, and 8; ITGB1, ITGB3, ITGB5, ITGB6, and ITGB8), each can interact with extracellular matrix ligands; the CD51 / Integrin alpha-V, perhaps the most studied of these, is referred to as the Vitronectin receptor (VNR). In addition to adhesion, many integrins are known to facilitate signal transduction (1).